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    <title>ShellCheck: SC2165 – This nested loop overrides the index variable of its parent.</title>
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    <h1>SC2165 – ShellCheck Wiki</h1>
    <a href="https://github.com/koalaman/shellcheck/wiki/SC2165">See this page on GitHub</a>
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    <h2
id="this-nested-loop-overrides-the-index-variable-of-its-parent">This
nested loop overrides the index variable of its parent.</h2>
<p>And companion warning "This parent loop has its index variable
overridden."</p>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2165.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="cf">for</span><span class="kw">((</span><span class="va">i</span><span class="op">=</span><span class="dv">0</span><span class="kw">;</span> <span class="va">i</span><span class="op">&lt;</span><span class="dv">10</span><span class="kw">;</span> <span class="va">i</span><span class="op">++</span><span class="kw">))</span></span>
<span id="cb1-2"><a href="SC2165.html#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="cf">do</span></span>
<span id="cb1-3"><a href="SC2165.html#cb1-3" aria-hidden="true" tabindex="-1"></a>  <span class="cf">for</span> i <span class="kw">in</span> <span class="pp">*</span></span>
<span id="cb1-4"><a href="SC2165.html#cb1-4" aria-hidden="true" tabindex="-1"></a>  <span class="cf">do</span></span>
<span id="cb1-5"><a href="SC2165.html#cb1-5" aria-hidden="true" tabindex="-1"></a>    <span class="bu">echo</span> <span class="st">&quot;</span><span class="va">$i</span><span class="st">&quot;</span></span>
<span id="cb1-6"><a href="SC2165.html#cb1-6" aria-hidden="true" tabindex="-1"></a>  <span class="cf">done</span></span>
<span id="cb1-7"><a href="SC2165.html#cb1-7" aria-hidden="true" tabindex="-1"></a><span class="cf">done</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2165.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="cf">for</span><span class="kw">((</span><span class="va">i</span><span class="op">=</span><span class="dv">0</span><span class="kw">;</span> <span class="va">i</span><span class="op">&lt;</span><span class="dv">10</span><span class="kw">;</span> <span class="va">i</span><span class="op">++</span><span class="kw">))</span></span>
<span id="cb2-2"><a href="SC2165.html#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="cf">do</span></span>
<span id="cb2-3"><a href="SC2165.html#cb2-3" aria-hidden="true" tabindex="-1"></a>  <span class="cf">for</span> j <span class="kw">in</span> <span class="pp">*</span></span>
<span id="cb2-4"><a href="SC2165.html#cb2-4" aria-hidden="true" tabindex="-1"></a>  <span class="cf">do</span></span>
<span id="cb2-5"><a href="SC2165.html#cb2-5" aria-hidden="true" tabindex="-1"></a>    <span class="bu">echo</span> <span class="st">&quot;</span><span class="va">$j</span><span class="st">&quot;</span></span>
<span id="cb2-6"><a href="SC2165.html#cb2-6" aria-hidden="true" tabindex="-1"></a>  <span class="cf">done</span></span>
<span id="cb2-7"><a href="SC2165.html#cb2-7" aria-hidden="true" tabindex="-1"></a><span class="cf">done</span></span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>When nesting loops, especially arithmetic for loops, using the same
loop variable can cause unexpected results.</p>
<p>In the problematic code, <code>i</code> will contain the last
filename from the inner loop, which will be interpreted as a value in
the next iteration out the outer loop. This results in either an
infinite loop or a syntax error, depending on whether the last filename
is a valid shell variable name.</p>
<p>In nested for-in loops, variable merely shadow each other and won't
cause infinite loops or syntax errors, but reusing the variable name is
rarely intentional.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>None.</p>
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